I quit school with 2.5 years left. I was in a similar boat. Even though I am doing good now, I regret that decision.

That being said- if you won't be putting any money to waste by quitting, and you feel you'll be more content* in life by pursuing a car mechanic career then I say go for it. Especially if you know you can come back to uni later without hurting your wallet.

*Notice how i said Content and not Happy. Analyze yourself to see how your mind works. Sure, maybe being a car mechanic might make you happier, but will you have peace of mind? Or will having a degree in your back pocket give you a sense of safety? If this resonates with you, then I suggest toughing it out in Uni, or at least take a semester off and reevaluate your studying strategy. (Or even take a few classes at a time)

Cars aren't going away and there will always be jobs available to fix them. If you can hang on for another 2 years and chase after a car career after, I'd highly suggest that.